This invention relates to clamps and presses that may be used in many industries and are suitable for finely controlled clamping and pressing of any materials including plastics, metal and timber.
In particular the invention relates to a clamp suitable for use with timber such as in the manufacture of items of furniture.
In furniture making and similar timber-working, solid timber is often glued edge-to-edge to form a solid timber panel, in which case pressure is applied to both the edges and faces of the panel. Additionally, in some instances flat panels of solid, ply and/or veneer timber are constructed by pressing the timber surfaces together. In this case pressure is applied only to the faces of the panel. Such flat panels often are used in the manufacture of doors.
Most commonly, the traditional type of clamp, known as a sash clamp, has been used in panel manufacture. However, it is very difficult to make quality panels by the use of this method because sash clamps were not designed for that particular purpose. The panels produced are almost always uneven.
In an attempt to improve that method of manufacture, a flattener is used. The flattener uses a system similar to a sash clamp to push down the surface of the panel to straighten it. The device can operate by pneumatic or screw means or by xe2x80x9cgeexe2x80x9d clamps. This, of course, adds an extra operation to the panel making process and can be very time consuming.
The applicant is aware of other methods to achieve the result of the present invention but they involve the use of complex and expensive apparatus. An example of such apparatus is known as a Mill Press, which has rotating frames all around and occupies a large amount of space. The use of a Mill Press is not limited to timber but generally a Mill Press will only be used by the larger factories because the cost of each press can often be more than AU$15,000.
Consequently, there is a need for a pressing device that is simple in its construction and operation and is able, if required, to press a panel of timber in two dimensions simultaneously.
The present invention seeks to meet this need.
This invention accordingly provides a clamp comprising:
at least two opposed first clamping surfaces, at least two opposed second clamping surfaces disposed perpendicularly to the planes of the first clamping surfaces, at least two opposed pressure-bearing surfaces spaced apart and located on longitudinal axes of the first clamping surfaces and disposed at an angle from the first clamping surfaces, and two rigid pressure-bearing points, one of said pressure-bearing points located to align when in use adjacent to one of the pressure-bearing surfaces and the other pressure-bearing point located to align when in use adjacent to the other pressure-bearing surface; and
means for imparting a longitudinal force such that the pressure-bearing surfaces are urged against the pressure-bearing points and, as the angled pressure-bearing surfaces slide over the pressure-bearing points in response to the longitudinal force, that longitudinal force is translated into a clamping force that urges the opposed clamping surfaces towards each other.
In a particularly preferred aspect, the invention provides a clamp comprising:
two opposed clamping components each having (i) a first clamping surface, (ii) a second clamping surface disposed perpendicularly to the plane of the first clamping surface, (iii) a pressure-bearing surface located on a longitudinal axis of the first clamping surface and disposed at an angle from the first clamping surface and (iv) a rigid pressure-bearing point located to align when in use adjacent to the pressure-bearing surface of the second clamping component;
means for imparting a longitudinal force to the clamping components such that the pressure-bearing surface of one clamping component is urged against the pressure-bearing point of the other clamping component and, as the angled pressure-bearing surfaces slide over the pressure-bearing points in response to the longitudinal force, that longitudinal force is translated into a clamping force that urges the first and second clamping surfaces of one clamping component towards the first and second clamping surfaces, respectively, of the opposed clamping component.
It is preferred that the pressure-bearing surface is disposed at an angle of about 60xc2x0. In some circumstances, where it is desired to alter the pressure applied to a work-piece, a more acute angle can be used. It is preferred that the pressure-bearing surface is fixed at a given angle but, alternatively, the clamping component may be adapted so that the pressure-bearing surface can swivel to provide a variation in angle. Alternatively, the pressure-bearing surface may be curved rather than linear to differentially exert pressure to a work-piece as longitudinal force is applied to the clamping components.
It is further preferred that there is a plurality of rigid pressure-bearing points arranged so that the two clamping components may be inter-engaged at any of the points thus allowing for the accommodation of work-pieces of varied sizes.
In a more preferred embodiment, the rigid pressure-bearing points are movable from one point along the length of the clamping component to a plurality of other points.
A first clamping surface may be provided by one of the upper edges of a U-channel member and an additional first clamping surface may be provided by the other upper edge of the U-channel member. It is preferred that a stop member, having a pressure-bearing surface and a second clamping surface, may be fixed within the U-channel.
Preferably the means for exerting the said longitudinal force is a pressure-exerting device comprising a clamping plate adapted to engage with and exert force against a second clamping surface and a pressure plate operably attached to the clamping plate and adapted to be advanced towards and apply pressure to a work-piece located in the clamp.
Preferably the clamp includes an allowance for height adjustment of a stop member and incorporates a pressure-exerting device with the stop member.
It is particularly preferred that the clamp includes a pre-tension member that in operation of the pressure-exerting device provides resistance against the pressure plate and thus begin the movement of the first clamping surface towards the work-piece before the work-piece is compressed against the second clamping surface. (Without this improvement, in some cases where the work-piece is bowed or uneven the compression of the second clamping surface against the work-piece does not allow enough relative lateral movement of the two clamping components to provide sufficient clamping force from the first clamping surface.) The pre-tension member comprises a bearing plate mounted perpendicularly on a slide that runs along a groove in the U-channel member against the bias of a spring that is attached to a stop pin.
An alternative use of the pre-tension member is obtained by positioning it distal to the edge of the work-piece so that the movement of the bearing plate is limited by the stop pin before the bearing plate bears against the edge of the work-piece. By this means there is no pressure against the edges of the work-piece but only pressure exerted against the faces of the work-piece by the first clamping surfaces.
A flange and locating holes may be provided on the stop member so that the stop member may be fitted into a pair of grooves in the internal surface of the U-channel member in a sliding manner and be locked into position by a locating pin passed through a locating hole on the stop member and a mating hole on the U-channel member.
In addition, a joining member may be provided with a pair of flanges adapted to fit within corresponding grooves within a U-channel member and to thus join two U-channel members end-to-end.
It is further preferred that the clamp is adapted to be mounted on a carriage for the purpose of ready and controlled positioning of the clamp such that a clamp can be positioned instantly to suit a particular work-piece and to maintain an accurate alignment (usually of 90xc2x0).